You mean like
this? I haven't actually used it myself, but looking over the AP, it looks like it should do what you want.
Note: This is different from the "Wireless AP Router", this is apparently just an AP. You'll still need a router on your network somewhere. I'm not sure if this hands out DHCP addresses or not, you'd have to check around.
Either way, to answer your question: Yes, it's possible to add an AP to your existing network without tossing a wireless router in.